Ca test kit reliability?

[sandyc]

Randy,

Would you please take a look at this thread http://archive.reefcentral.com/forums/showthread.php?s=&threadid=479748 and let me know what you think about the test kit in question for Ca? The results I list for Ca and Mg were run by ICP under rather strict QA procedures in a Certified lab. In other words, I trust these results over the Sea Chem test kit. I am dissapointed in the test kit's results. Thanks for your input.

[Randy Holmes-Farley]

Do you know what sort of ICP was used, and the exact protocol? If it is not intended for seawater, I wouldn't assume that it is necessarily perfectly accurate. I recall at one point Habib (owner of Salifert) said that ICP was not very accurate for calcium, although i did not explore his exact concerns.

It is also possible that the kit is off.

[Navyblue]

The error margin of ICP (though I'm not sure of the new advancement) is preety large IMO, not considering the tons of interference in salt water matrix. I'm not an ICP expert but IMO it is definitely not an easy task to analyse salt water with ICP, especially without a protocol specifically for salt water.